Plaster



V V "PLASTER Vito G. Busatti, New York, N. Y.; Josephine Busatti, admiuistratrix of said VitoG. Busatti, deceased No 'Drawing. ApplicationDecember 31, 1952 Serial'No: 629,120

6 Claims.- (Cl. 106-114) This invention :relates to a-plastercotnposition' and is a continuation-impartofmyiapplication S'er. No. 145,089, filed February 18, 1950, now abandoned.

In the ordinary application of plaster to produce a smooth wall or a ceiling, it is customary to apply-several coats of 'diifere'nt compositions,- only "the last of which is a w hite'or finish plaster' to give the desired smooth, White surface. This conventional-process has s'erious practical limitations. For example, -the base j or brow -coats of plaster applied informing a'wall or a ceiling must each be allowed to dry 'be'forethe ne'xt coat is applied so that the final plaster wall will 'not quickly fo'rm cracks and checks. Not only' does' this procedurebuild up an unnecessarily thick'se'ction of plas'ter'but it also means that the plasterer, whose time-is valuable, must come at three diiferent times and each time-set up 'his'equipment' and go through the complete operation of preparing and applying aco'atof plaster. p I

Another drawback to 1 this fcbnventional procedure is that theplaster must be applied quickly and worked into position within a short time. Variousfcommercialretarders toslow' down'the setting o'f' theplaster are available but have limited application and'usu'ally'fspoil' the plaster mix if added in excess. g

In many instances it has become so diflicult and expensive to produce plaster ceiliiigs that 'lalrge building projects have formed the ceiling from molded concrete Without any .attemptto obtain-a plasterceiling.

It is an object of this invention to-provide aplaster composition which overcomes these and other disadvantages and which can be appliedin one or more' ico'ats to give a finished wall or ceiling surface with-a; superior finish.

Another object of the invention is-to apply such a composition so that great savings can be effected in producing plastered walls and ceilings. N

I have discovered that a plaster composition made with the usual amounts of lime and plaster of Pafiscan be greatly improved by including? inthe composition boric acid as a setting rate retarding agent and starch. The starch may be in the" form of rice flour or the boiled juice or steepings 'obtained'froni rice 'flduralthotigh other forms 'ofstanch 'such as'cornsta'rclrrnay be-usedf In' most plaster compositions the lime and plaster of Paris are used in'the proportions of about 5 bags "oflime to 1 bag of plaster of Paris. I have found'tliatfthese proportions are not at all priticalwhenflbofic acidand starchare added in accordance with my invention. For example, the starch addition makes it possible'to use less than 1 part plaster of Paris to'4 parts limeand'stillobtain a fiinished plasterthatfibes 'not crackfand is superior in many of its properties to a conventional mixture. -Or, the proportion of plasterof Paris can be increased to an amount equal to" or evenin excess of the amount of lime in accordance withmyinventionprovided proper amounts of boric acid and starch are also added-to control-the rate'and characteristics of setting or the; plaster. Inprdina'ry-pl'aster;"of'"eoufse; The mount of plaster of Paris United States Patent ice be included in the composition to improve or alter its properties or to adapt-it for'some particular-application. For example, it may be advantageous under many'condi tions to use a substantial'proportion of finely divided relatively. inert materials such as white sand, marbledust, asbestos fibres, hair, wood fibres and the like.- Other optional ingredients of the composition include small amounts of Keenes cement (hard calcined gypsum), alum and an adhesive that has some flexibility whenhardened such as an adhesive made from pyroxylin or one or more of the cellulose or vinyl esters.

Even withoutany of these various optional constituents, I have'found that my plaster composition is capable of being applied very advantageously as compared with-0rdinary plaster mix. Boric acid used as a retarder has particular merit because it can be used in an amount to slow down the setting rate of the plaster very substantially without producing serious cracks or checksin the hardened plaster. Also, if boric acid is added in excess, of What is needed the plaster mix is not spoiled. The starch adds a considerable flexibility and toughness to the final coat enabling the application of much thinner coats than would normally be applied. It also has some retarding efiect on-the setting rate and'makesunorthodox applications possible. For example,'a wall prepared with wood or wire lath can be given a coat of ordinary plaster and-then a finish coat of plaster of my invention can be applied without waiting more than about 15 minutes and without producing objectionable cracks. v a

Whether this plaster of my invention is applied to form a ceiling or a wall, the presence of the boric acid and starch, even though they may be present in small amounts, prevents the plaster from peeling ofif when it is applied with a trowel. The trowel slides easily and smoothly,

does not leave a rough surface and the fresh plaster is much easier .to join to analready hardened-plaster-section. Because of the greater elasticity, smoothness and easier workability of the plaster of'this composition, it can be". applied in a verythin coat and thus a given quantity of the composition can beused to coat a much larger than normal surface.

This composition can also be applied, unlike ordinary plaster, directly .to a surface ofconcrete, stone or the like, although when applied to such a surface it is usually best to include in the composition additional ingredients, such as marble dust and Keeneslcement or some other adhesive to give the plaster greater adhesion to the surface. I

In addition to the application of my improved plaster compound in' the usual manner, it may also be applied in making walls or ceilings by a molding operation. For example, in forming a ceiling, themold used, which usually is constructed of wood, may be first coated with,

lath or other porous form members to hold a brownor,

concrete mixture in place and a white plaster finish can be obtained by jpouring'thelplaster composition of my invention between the surface of an outer form and such porous Wall lath form. a

The following compositions are given by way pfijeX- ample but the invention is not intended to be limited This can be done to ,giveeven though 'which is very desirable but not essential.

thereto sinceiit will be apparent to those skilled in the I Lirne -t 1000 Plaster of Paris.. 150 White sand l 200 Boric acid 1 Rice flour 5 The "foregoing composition contains substantially less plasterof Paris than is customary andincludes white sand The amount of boric acid can be varied considerably depending upon the amount of the retarding effect that is desired. In the 7 If the composition of my invention is to beapplied directly to a rough surface, such as concrete or stone, or if it is to be applied in theformation of a ceiling, it may be desirable to add to it 'a small amount such as (based on the weight of lime) of a flexible adhesive such as one of the pyroxylin or cellulose ester adhesives readily available on the market. This. gives the plaster much greater-adhesion when applied to such surfaces.

Plaster compositions of my invention may be made up, of course, by mixing the'various ingredients together at the site where the plaster is to be used. Such compositions may also be mixed dry and in this form include, except for water, all or most. of the ingredients needed in the final plaster mix.

proportiongiven, the composition can be readily worked for about 3 to 4 hours compared with the usual plaster composition which has to be fully applied in about /4 of an hour. The quantity of rice powder can be varied substantially and can eitherbe added to the composition in the form of a powder or flour, or it can be boiled T and the steepings or juice added to the plaster composition.

Example ll.-Another plaster using less than the normalamount of plaster of Paris is as follows:

Example 1lI.-Aplaster using considerably more than the conventional amount of plaster of Paris can be formulated as follows:

Parts by weight Lime 800 Plaster of Paris t 600 Boric ncirl l 4 Rice flour or cornstarch '32 Based on 1000 parts of lime, I may use plaster of'Paris in an amount that is considerably more or less than the conventional (of the weight of lime). In fact, the amount of plaster of Paris may vary all the way from 5%*toeven 200% of the weight of the lime. In general an amount that is 25-50% of the lime is very satisfactory. The amount of boric acid used will vary depending upon the proportion of plaster of Paris, the setting rate desired, and to a lesser extent the amountof starch. In general the amount of boric acid used will fall within the range of 0.1% to 3 or 4% "of the weight of the plaster of Paris. If plaster of Paris is used in larger than normal amounts, the amount of boric acid should be increased to keep the plaster from setting too quickly. Increasing the boric acid in any given formula slows down the settingrate. An. excess of boric acid may delay too much the hardening ofthe plaster but will not otherwise be objectionable,

The terms and expressions which I have employed are used as terms of description and not of limitation, and I have no intention, in the use of such terms and expressions, of excludingany equivalents ofthe features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invention claimed.

1. A wall plaster composition suitablewhen mixed with water for application, to a surface with a trowel in a single coat and also for, application in more thanone coat without waiting for the underneath coat to dry, said composition consisting essentially .of lime and plaster of Paris as its, principal constituents, the plaster of Paris being presentin an amountfrom 5 to 100% 'of the weight of the lime, boric acid as a setting rate retarder in an amount of from 0.1, to 4% of the weight, of the. plaster, of Paris, and starch in an amount of. from 0.3 to 10% of the weight of the lime, said composition being characterized by ease of application when applied with a trowel and great resiliency, toughness and strong adherence to surfaces on which it is applied after setting.

2. A composition as defined in claim 1 in whichthe starch is rice, powder.

3. A composition ,asdefined in claim 1 in which the. starch is cornstarch.

4. A plaster composition which consists of the following as its principal active, ingredients in approximately the following proportions: M a

, H Parts Lime 1000 Plaster of Paris -t 150 Boric acid 1 Rice flour 5 in the amount of 0.3m 10% of the weight of the lime 5. A plaster composition which consists of the following as its principal active ingredients in approximately the following proportions:

. 6. A wall, plaster composition consisting essentially of plaster of Paris and lime and containing more plaster of Paris than the usualproportion of 1 part plaster of Paris to 4: parts lime, said, composition also containing starch and boric acid in an amount'of ,O.1 to 4% of the weight of the plaster-of Paris, and said composition when mixed. with waterv being, capable of; easy application with a trowel and after setting being characterized by its exceptional resiliency, toughness and adherence to the surface on which it is applied. v i

j References Cited in the file of this patent UNITED STATES I PATENTS 387,519" Key Aug. 7, 1888 482,544" Casselman Sept. 13, 1892 5 Summers Apr. 14, 1896 Summers Apr. 14, 1896 Walper Nov. 16, 1926 Wiggin et a1. Oct. 22, 1929 Jurgensen Ian. 13, 1942 Swayze Apr. 24, 1945 Hoggatt Nov. 6, 1945 Eberl June 19, 1951 FOREIGN PATENTS 10,130 Great Britain Dec. 17, 1914 OTHER REFERENCES 7 

1. A WALL PLASTER COMPOSITION SUITABLE WHEN MIXED WITH WATER FOR APPLICATION TO A SURFACE WITH A TROWEL IN A SINGLE COAT AND ALSO FOR APPLICATION IN MORE THAN ONE COAT WITHOUT WAITING FOR THE UNDERNEATH COAT TO DRY, SAID COMPOSITION CONSISTING ESSENTIALLY OF LIME AND PLASTER OF PARIS AS ITS PRINCIPAL CONSTITUENTS, THE PLASTER OF PARIS BEING PRESENT IN AN AMOUNT FROM 5 TO 100% OF THE WEIGHT OF THE LIME, BORIC ACID AS A SETTING RATE RETARDER IN AN AMOUNT OF FROM 0.1 TO 4% OF THE WEIGHT OF THE PLASTER OF PARIS, AND STARCH IN AN AMOUNT OF FROM 0.3 TO 10% OF THE WEIGHT OF THE LIME, SAID COMPOSITION BEING CHARACTERIZED BY EASE OF APPLICATION WHEN APPLIED WITH A TROWEL AND GREAT RESILIENCY, TOUGHNESS AND STRONG ADHERENCE TO SURFACES ON WHICH IT IS APPLIED AFTER SETTING. 